twin 454' s

[ralphspa]

:2purples: Hey Guys
I just bought a Wellcraft Scarab Panther 30' with twin bravo setup.The engines are missing, so i am looking to rebuild two engines as economical as possible.I am familiar with rebuilding engines but i would like to get 375-400 hp out of each 454 that i hope to find soon as a winter project.The hard part for me is cam and head selection since i am not familiar with performance modifications.As far as i know oval port heads are good enough but im not sure about valve size requirements or cam duration/lift requirement.If i use an automotive block i understand that i will need forged pistons,but are hypereutectic pistons also acceptable? Do i need dome pistons to get to 375-400 hp? I was hoping to go with a non rollerized block if possible to keep the cost down.What size carbs would i need 750CFM or 850CFM?
Does anyone out there have one of these boats?just wondering what kind of speed to expect to get? Not to sure how heavy the boat is?Also if anyone has a used complete drop in motor i might be interested in bying one since i will need all the accessories for these motors i.e. intake/flywheel,brackets,balancers,carbs and water pumps.
Thanx Ralph

[ECeptor]

Go online and buy this book - "Big Block Chevy Marine Performance" by Dennis Moore.
It is a great overview plus had details about performance modifications. Well worth the relatively small investement.

[SmokinLowriderSS]

400 HP out of a 454 is easy, I'll be there with a very (nearly) stock motor when my headers go on this winter ($2,000 away). Here's my combo, I think something very similar would work well for you even though mine is in a jet. I have specs from Desktop Dyno program I'll show ya that I think she'd spin a prop hard just as she does my Berk pump.
454, 2-bolt, cast crank & pistons, stock steel rods (I istalled ARP bolts and had them resized) 8.5:1 or so compression (estimated)
353049 late 70's large oval port, open-chamber (122cc) heads, stock valves (.208/.176), stock valvetrain (long-slot rockers), 3/8" pushrods. A performance machine shop locally says these and the '781 heads which have the same specs, are beautiful to port. They get to NEXT winter.
Special cut Iskendarian cam from DuaneHTP he likes for jets. .565" lift, 280* duration, hydraulic but the ramp rates are higher than Isky's standard cams, Isky superlifters & springs, Polylocks on the rockers.
Edelbrock Performer RPM Air Gap manifold topped by a 700 CFM Holley 4150.
It starts great (cold-blooded first light of the day but just touch the key later on, all day), idles lopey but under controll at 850RPM, even a hard throttle slam has no holes or soggy/soft spots. She just instantly winds up till the pump stops her at 4800 RPM.
My DD Specs, they are very close to what Impeller info says it takes to spin my drive so I believe them.
My current info through my log manifolds, condensed a bit.
Torque: 381@2500 412@3K 421@3500 413@4K 394@4500 357@5K
Horsepower: 281@3500 315@4K 337@4500 340@5K 317@5500
With my headers (anticipated)
Torque: 418@2K 443@2500 453@3K 460@3500 463@4K 452@4500 425@5K
HP: 307@3500 352@4K 388@4500 404@5K 394@5500 364@6K
Same Setup with a stage 1 porting and larger stock size valves (.219/.190)
Torque: 415@2K 443@2500 457@3K 474@3500 489@4K 497@4500 491@5K 468@5500
HP: 316@3500 373@4K 426@4500 467@5K 490@5500 488@6K
In this day of a 500/502 being sought after, that looks mighty close to a 500/500/454 .... and on 8.5:1 flat-tops.
My orriginal engine build was about $1,800, and that included the $400 cam kit and $290 manifold. The headers will cost me $2,000 or so. The porting job next year looks like arround $1,100 or $1,200 with valve replacements.

[ralphspa]

Thanx for the help guys,
I've already looked into buying dennis moores book. As for comparison with a jet drive im wondering if a jet drive wouldnt be under as much a constant heavy load as a merc drive.The jets love to rev a bit higher dont they,so i believe the cam selection should be different? I just bought a 4 bolt main block with two automotive heads (head castings:14092360 oval port) Would these be acceptable for 350-425 HP range if better springs/rockers were installed?I understand that stock rods and hypereutectic pistons are also acceptabe.By the way my heads only have 2.07 Intake and 1.70 exh valves are they a bit small?
Thanx ,Ralph

[SmokinLowriderSS]

14092360...86-90...oval...OPEN...454 Truck, "peanut" round ports
EWWWWWWWWWwwwwwwwwwwwwwww. Peanut ports. Not good for HP but good torkers. Chokes a motor hard above about 3500 RPM. I'm afraid they'll dissapoint you. It's an open chamber so likely somewhere between 110cc and 123cc chambers. With flat-top pistons you look at 8.5 to maybe 8.8:1 compression. You'd be better off with one of the large oval port heads, even with the "small" stock valves. I'm running those valves, 2.06" / 1.72" The factory rods are fine, good steel, but, you likely have the knurled 3/8" bolts. I would go to ARP and get new ones and have the rods resized to match again. Insurance is a set of 4730 Wave-locs installed properly. Much tougher than the orriginals, $60 for the bolts, cost me $90 to have rods resized, pistons on.
Jet pumps are just Dynos with an outlet and an endless supply of water to feed them, They work a motor hard. I am only spinning mine 4800RPM, max. The pump says I don't have enough to spin more, unlike a prop which can allow some "winding" to occur on acceleration at top speed. I was thinking mine would work as my torque curve is big and solid, just what a prop drive needs worse than my jet which, yes, blows right through my torque curve to max-load the pump.
My torque level still governs how fast the motor winds up on the pump and helps the HP spin the pump. I think mine is a good setup, for whatever final drive it is attatched to. I have not tried to make mine a hi-spinning race motor, it is a solid, muscle motor with power everywhere and lots of it (more coming every winter). Next spring I should be pulling over 450 pound-feet of torque from 3,000 all the way to 4500 RPM. With a head porting, nearly 500 '/lbs of torque, from 4,000 to 5,000, right where even most I/O motors run stock.450 pounds all the way down to about 2,600 RPM.
I saw A real strong hot-motor on the board once, a 502 with 700+ HP and 600+ torque that couldn't spin a pump similar to mine, with the same impeller cut I have above 4,000 RPM. ALL his power was above 4500 RPM and he could not get to it. I could actually out-power him, torque and HP untill 4500 RPM. I'd have been able to outrun him too in even a light race hull I believe, just because he couldn't spin the pump and I could. :mix:
Best of luck to you.

[ralphspa]

Thanx for the info sofar! I guess ill be on the hunt for 4 identical heads that are going to be better.Anyone got any for sale?i just won the dennis moore bb chev marineperformance book from ebay.ill see if there is any good info for me in there. :idea:
unfortunatly my hunt is going to be quite painstaking.i still have to find manifolds,crank,flywheels,dampers,tstat housings ,wiring etc unless i find complete assemblies with bad motors.

[SmokinLowriderSS]

Look over those torque specs of mine again. It has a lot of muscle down low and a really fat midrange pull. Yes, those specs aren't so important to a jet that blows right through them to reach the point the jet drive "dyno" says "Is that all the motor you got?" but I think this 454 of mine would pull a prop quite well through the 3,000 to 4,500 RPM range, even on a pretty heavy boat.
The smaller valves help the torque and keep it lower in the RPM range, They do choke it a bit above 5K tho, fortunately, not nearly as badly as a set of pickup truck "peanut" small oval port heads.
I'm running flat-top pistons, an aftermarket manifold, a relatively mild hydraulic performance cam, and a 700 CFM holley - 350HP
Add a set of good exhaust system to let her breathe to her ability, 400HP.
Headwork to increase her breathing again, 480 HP / 490 pound feet torque, at aprox 8.5:1, 87 octane, all of it usable to a prop I believe. :idea:

[SmokinLowriderSS]

Oops, my earlier post didn't show up untill I posted my previous post. Grrrr Thought I had typed all that oner of these 12-hr days and lost it. The "shortened" version above reads a bit snippy, it should not, sorry.
Good luck on the parts search, doubled. I have a cast iron dual plane Big Block GM special available :wink: (intake manifold), also an oil pan and timing cover (both stock). They were pretty rusty at the joining area (about 6" either side of the seal surface (seal area unharmed)) so I decided to replace them on e-bay. De-rusted, primed & painted the oil pan, timing cover is still on the wall. I have a holley carb spark arrestor too I am not using since going to K&N. :cool:

[paradigm shift]

Here are a couple of nice proven run packages. These are not super cheap but a nice package for the money in my book. Just depends on your budget constraints.
Good luck with your build up. Forged will stand up better to adverse conditions. (Detonation will kill hypereutectics).
Here's the Federal Mogul parts list for a 454+.030, which dyno'd at 505 chp@5500;
L2465F+.030 forged pistons, 9.6:1 c/r
E233K+.030 rings
4400M main brgs
3190CP rod brgs
1404 cam brgs
381-8009 brass core plug set
KT3-171S timing chain set
CS1140R cam, 234intake/244exhaust@.050, .553/.578 lift
HT817 lifters
VS1581 valve springs
VSR7015 retainers
VK338R keepers
V-8007R intake valves, 2.19 dia.
V-8006R exhaust valves, 1.90 dia.
Merlin oval-port heads, Performer intakes, Holley carburation
These did not see a dyno.
Engine 1 has H693CP+.030 hypereutectic pistons, 9.5:1. All other components are as listed above, including cams. (I think this is pushing the limit for hypereutectic pistons in my opinion for reliabilty. Just my .02.)
Engine 2 has H426CP+ .060 hypereutectics, 8.6:1 and a slightly smaller cam, CS1139R, 224/232@.050, .527/.553 lift, GM rectangular-port heads, GM aluminum intake, Holley carb, all other components are the same.
Engine 3 also has H426CP hypereutectics, he used an Ultradyne cam(virtually the same #'s as the CS1139R), GM rectangle-port heads, GM aluminum intake, Q-jet carb. All other components as listed.